Evidence is mounting that the U.S. defense community and the Obama administration view 2013 as the likely window for a bombing attack on Iran's nuclear and missile facilities.

It could be earlier, timed to use the chaos of the Syrian government's fall to disguise such an attack, or later, if international negotiations with Iran stretch out without failing completely. But there is evidence that Iran's intransigence over shutting down its uranium-enrichment program will not buy it much more time.

Because of these shifting factors, military planners and White House advisers are still debating the advisability of a kinetic attack on Iran even though they say that option is ready. Three questions need to be answered: